miss nelson science ~ chapter 9 climate. currents and climate section 2
TRANSCRIPT
Miss Nelson
SCIENCE ~ CHAPTER 9
CLIMATE
Currents and Climate
SECTION 2
Have you ever heard a story about someone finding a message in a bottle that was thrown into the
ocean?
How did the bottle travel all the way to them?
ANTICIPATORY SET
S 6.4.d –Students know that convection currents distribute heat in the atmosphere and oceans
S 6.4.e –Students know differences in pressure, heat, air movement, and humidity result in change in weather
STANDARDS
What causes surface currents and deep currents?
What effects do they have?
THE BIG IDEA
El Niño –A climate that occurs every two to seven years in the Pacifi c Ocean, during which winds shift and push warm water toward South America
La Niña – A climate in the eastern Pacifi c Ocean in which surface waters are colder than normal
Salinity – The total amount of dissolved salts in water
Upwelling – The movement of cold water upward from the deep ocean that is caused by wind
Coriolis eff ect – The eff ect of Earth’s rotation on the direction of winds and currents
KEY TERMS
Read Currents and Climate on page 356 of your textbook
CURRENTS AND CLIMATE
Surface currents (which affect water to a depth of several hundred meters) are driven mainly by winds
SURFACE CURRENTS
Most of the currents flow east or west, and then double back to complete a circle
View Figure 8 on pages 457 of your textbook
SURFACE CURRENTS
Winds are caused by differences in air pressure
Differences in air pressure are the result of the unequal heating of the atmosphere by the sun
The sun’s radiation (of heat) is the ultimate source of energy that powers global winds and surface currents in the ocean
SURFACE CURRENTS
Global winds are not the only factors that influence surface currents
Continents block and redirect the flow of currents
Coriolis effect also influences surface currentsCauses global winds to curve as a result of Earth’s rotation
CORIOLIS EFFECT
A surface current warms or cools the air above it, influencing the climate of the land near the coast
EFFECTS ON CLIMATE
Warm-water currentsWinds pick up
moisture as they blow across
Cold-water currentsCool the air
above themCold air holds
less moisture – these currents tend to bring cool, dry weather to lands in their path
EFFECTS ON CLIMATE
Read Surface Currents on pages 357 – 358 of your textbook
SURFACE CURRENTS
El Niño and La Niña are short-term changes in the tropical Pacific Ocean cause by changes in ocean surface currents and prevailing winds
El Niño is a warm-water event that disrupts the cold ocean currents along the western coast of South America Effects weather patterns around the world
La Niña is the opposite – when surface waters in the Pacific are colder than normal Brings colder than normal winters and greater
precipitation Causes hurricane activity in the western Atlantic
EL NIÑO AND LA NIÑA
Read El Niño and La Niña on page 359 of your textbook
EL NIÑO AND LA NIÑA
Deep currents are caused by differences in the density of ocean water
DEEP CURRENTS
The density of ocean water depends on its temperature and its salinity
OCEAN WATER DENSITY
View Figure 11 on page 360 of your textbook
OCEAN WATER DENSITY
Deep currents move and mix water around the world
They carry water from the poles toward the equator
A GLOBAL CONVEYER BELT
Deep currents flow SLOWLY
May take as long as 1,000 years to flow from the pole to the equator and back again
A GLOBAL CONVEYER BELT
Read Deep Currents on page 360 of your textbook
DEEP CURRENTS
Upwelling brings up tiny ocean organisms, minerals, and other nutrients from the deeper layers of the water
UPWELLING
In most parts of the ocean surface waters do not usually mix with deep ocean waters
Mixing sometimes occurs as winds blow away the warm surface water and cold water rises up to replace it
Without this motion the surface waters of the open ocean would be very scarce in nutrients
UPWELLING
Upwelling occurs in the Pacific Ocean off the west coasts of North and South America
The arrival of El Niño prevents upwelling from occurring
Without the nutrients brought by upwelling, fish die or go elsewhere to find food
UPWELLING
Read Upwelling on page 361 of your textbook
UPWELLING
Surface currents are mainly driven by what?
What causes deep currents?
CHECK FOR UNDERSTANDING
Surface currents are mainly driven by what?Surface currents are driven mainly by winds.
What causes deep currents?Deep currents are caused by differences in the density of ocean water.
CHECK FOR UNDERSTANDING
Complete the Modeling, Guided Practice, and Independent Practice
Sections of your Climate 9-2 Worksheet.
MODELING / GUIDED / INDEPENDENT